Combining the Celsius Layered Structure FEA and 3D CFD workflows to perform PCB thermal analysis

Finite Element Analysis (FEA) is instrumental in performing a detailed simulation of conduction with boundary conditions of heat transfer coefficients (HTC) for effective convection and radiation.

In the Celsius Layered Structure (2.5D) FEA engine, if a PCB thermal analysis needs to include detailed cooling effects from the use of a fan and chassis, a CFD simulation is needed to capture the air-flow simulation. The Celsius LS-CFD workflow allows the quick creation of a thermal model in the CFD solver. Then, CFD results can also be imported into the Celsius LS FEA, updating the empirical correlation-based boundary conditions with the actual flow simulation results from CFD, if needed.

Here is the Celsius LS-CFD workflow diagram:

Consider a PCB with numerous components, and the largest among them is the U99, with high heat dissipation. 

You would like to cool it down during its electrical operation to optimal levels, with the fan cooling and chassis built up to do the combined FEA-CFD analysis.

Initially, the fundamental set up to perform the FEA includes:

• Importing the board layout to Celsius LS
• Material definition for all objects
• Defining thermal components and their heat dissipation values
• The current consumption of components
• Ambient temperature and setup of simplified CFD model option

At this stage, look at the results, which might startle you.

The maximum temperature is 166°C!

This is for the U99 component for the natural convection case of 0 m/s at 25°C ambient temperature in the 3D-T plot.

This high temperature is considered unacceptable, and fan cooling has to be utilized in the CFD solver to bring down the maximum temperature.

In the Celsius CFD, a few things that need to be done are as follows:

• Set up of the chassis fans, vent openings, and air chamber (including the material and emissivity values)
• Ambient temperature and other simulation options (static)

Now, the maximum temperature is 58°C for forced convection with fan cooling in a chassis environment.

This is cool!

The Celsius LS FEA-CFD workflow enables you to run an airflow simulation with a fan and chassis by importing the necessary thermal modeling information from Celsius LS into CFD. If needed, the CFD results can be brought back, further refining the boundary conditions in Celsius LS.

To run these Celsius LS-CFD simulations yourself, click here to access the RAK on How to Utilize a Celsius Layered Structures-CFD Workflow for PCB Thermal Analysis.